In the field of cutting devices, there is an abundance of prior art covering well known techniques of cutting with metallic blades, and substantial art in various types of circular blades, extended band saw blades, anvils and mechanisms for loading, adjusting, etc.,. Circular blade cutting (and slitting) is achieved transversely and longitudinally with shear cutting and/or score or pinch-type cutting devices.
For the numerous applications requiring longitudinal cuts, the art is crowded with disclosures of slitting blades and associated devices such as anvils, anvil holders and blade sharpeners. Transverse cutting devices and arrangements are also covered in many prior art patents, and special machines and apparatus are employed to make transverse cuts while the material is moving, or is capable of being moved forward between transverse cuts.
Certain devices also teach the stoppage of web material for the purpose of making transverse cuts during a dwell portion of the cycle, for example, U.S. Pat. Nos. 3,370,496 and 3,456,540.
There are numerous product uses (and substantial prior art) requiring cutting of apertures in the material, and/or, cutting of materials into special shapes. However, with these special shapes and apertures, prior art teachings lead into a class of disclosure that generally involves separate, non-continuous punching, forming and/or cutout operations and devices, or alternately, rotary devices which include specially shaped dies co-acting with a second anvil cylinder that can be hardened, or has hardened inserts of special shape. It is well known that when using rotary cylinders, cutting or shaping operations that are in register with the length of the cut piece will necessarily be a function of a repeat length substantially equal to the circumference of the cylinder or a multiple thereof, and hence, a given pair of cylinders is thereby limited to a single repeat length. When product length (repeat) changes are not a multiple of circumference, a new pair of cylinders is required, together with gearing and other associated drive parts, and this often involves a costly inventory of change parts. The expense of setup for length changes involves the cost of labor, but more significantly, valuable and costly lost production, and this total cost often dictates "minimum orders" or piece runs that are required for economical production.
In this invention, certain devices and methods are disclosed which can substantially minimize changeover time with the beneficial result that shorter production runs become economically feasible.
When using rotary cylinders for punching operations to make apertures in a material, there is a narrow range of "working depth" or "working diameter" that is permissible before there is a mismatch between the cylinder working diameter and the gear pitch line, and with greater depth, severe die or drive gear wear occurs.
It is accepted in the trade that even under optimum conditions, mechanical elements such as blades, anvils, dies, inserts, . . . etc., are subject to high wear and need frequent sharpening or replacement.
In the field of cutting shaped objects, prior art teachings are much less abundant, but certain art exists, for example, U.S. Pat. No. 3,381,563.
Considering the use of blades and anvils, or dies and coacting rolls, it becomes evident that precision alignment is difficult to achieve at original setup and is difficult to maintain during running, said effect resulting in speed limits vis-a-vis acceptable product quality control. Additionally, the initial expense of curvilinear cutting dies is very high because of the hardness required for life factors, and the resultant difficulty of machining for high precision mating relationship with the co-acting roll.
In recent years, the development of new cutting devices and their commercial adaptability makes new techniques possible. New cutting devices, for example, laser beam or water jet cutters will be referred to hereinafter as "impact beam" or "impact jet" cutting devices.
Because these cutters penetrate the material at a small point (as opposed to a line or a portion of a line), these impact type cutters can be used as part of a cutting apparatus wherein the cutter is translated in different directions at a pre-selected uniform, or variable, velocity, in combination with devices that permit uniform or non-uniform velocity of the material being cut, these motions and velocities allowing complete flexibility regarding the cut line shape and configuration at slow speeds. Design limits may make the cutting of certain special shapes impractical at higher speeds.
This invention differs from prior art by disclosing the positioning of the cutter over the material being cut while the material is moving.
The closest prior art teaching appears in the December, 1976 issue of MECHANICAL ENGINEERING (pp 40-44). The principle difference over the apparatus therein described is the inventive combination of a plurality of in-line cutters working in in combination with a web in motion, and the subsequent modification of the velocity of the cutter supporting framework due to web movement. A second basic difference between this disclosure and the movable cutter in the above-mentioned article is the use of a plurality of cutter-supporting frames, or the use of at least one cutting device on each of a plurality of frames, alone, or in combination with stationary cutters that produce straight line cuts as the web moves past same. A third basic distinction is the disclosure of modifying the velocity of the moving material as it passes through the "effective cutting zone."
It is understood that the embodiments shown for "interrupted" jet stream cutting can be rearranged in any embodiment using an intermediate diverter or baffle to produce a discontinuous cutting stream, or if design factors permit, the actuation of external means that turns the impact type cutter on or off as desired.
In the detailed description, it will become apparent that while the inventive system describes a completely flexible system for cutting any shape, there are a great many variables involved, and these factors are related and often dependent functions that affect the maximum speeds attainable.
While this inventive disclosure defines inter-related variables, it will be appreciated that each variable is a range of values as defined by certain practical and/or mechanical design limitations. However, minimum and maximum values can be assigned, and through comparative evaluations, optimum operating speeds can be determined.
In practical terms, and in order to minimize considerable engineering design effort required for each application, this inventive concept very beneficially lends itself to servo-loop electrical systems and computer programming. It is within the scope of this invention to determine and construct a suitable program such that the limits imposed on dependent and independent functions are evaluated by a computer and will then direct proper output signals to each of these functions to automatically adjust the mechanism involved to yield optimum speeds.